Mechanism for artificial legs



Nov. 14, i950 H. SARTIN MEcHANIsM FOR ARTIFICIAL LEGS 2 Sheets-Sheet l Filed June l5, 1948 llllll lllllll l ||||||l Fig' 3- RN 2 mn WIM J .l m M #A Y 7 B 4 j z .3 Mp2 H s Z lfm Z MMU.. www o I 3 WIM-.r .wenn Z Nov. 149 E950 H, SARTHN 2,529,958

MECHANISM FOR ARTIFICIAL LEGS Filed June l5, 1948 2 Sheets-Sheet 2 INVEN TOR.

f4/V351. SAPT//V BY Patented Nov. 14, 1950 UNITED STATES PATENT* oF Fics 4 Claims.

This invention relates to improvements in mechanism for artificial legs, and more particularly to an improved, spring-operated mechanism for controlling the foot and knee action of an articial leg.

It is among the objects of the invention to provide an improved internal mechanism for an artificial leg which mechanism supports all of the weight and other forces imposed on the leg and carries the hollow shell for giving shape and a substantially normal appearance to the leg, which includes a two-part foot piece and upwardly-extending strut bars pivotally connected to the foot piece and is spring operated to give a normal walking action to the foot piece, which permits relative movement of the two parts of the foot piececunder pressure to substantially the same extent as the movement of a natural foot, and positively returns the two parts of the foot piece to a substantially straight condition when the pressure is relieved, which Will not lock or bind in operation, can 'be readily modied to suit the requirements of wearers of different heights and weights, is adjustable to compensate for moderate variations in weight and other factors, and which is simple, strong and durable in construction, economical to manufacture, extremely light in weight, neat and attractive in appearance, and closely simulates the appearance and action of a natural leg.

Other objects and advantages will become apparent from a consideration of the following description and the appended claim in conjunction with the accompanying drawings, wherein:

Figure l is a longitudinal, medial cross-section of an articial leg mechanism illustrative of the invention;

Figure 2 is a longitudinal cross-section taken substantially on the line 2-2 of Figure l, and in a plane substantially perpendicular to the plane of the cross-section illustrated in Figure l;

Figure 3 is a bottom plan view of the foot piece of the mechanism, a portion being broken away and shown in cross-section to better illustrate the construction thereof;

Figures 4, 5 and 6 are side elevations of the improvedartificial leg mechanism showing the mechanism in three diierent operative positions; and Y Figure 7 is a longitudinal cross-section of the foot piece taken substantially on the line I-'I of Figure 3.

.With continued reference to the drawings, the improved artificial leg mechanism comprises, in general, a two-part foot piece II), a shank II pivotally connected at its lower end to the foot piece, spring mechanism I2 carried by the shank and operatively connected at its lower end to the foot piece, and a thigh boot I3 pivotally connected to the upper end of the shank I I.

The axes of the pivotal connections between the two parts of the foot piece, between the lower end of the shank andthe foot piece, and between the lower end of the thigh boot and the upper end of the shank are all substantially parallel to each other.

The foot piece I0 comprises a hollow rear part I4 providing externally thereof a heel I5, an arch I6, and an instep II and a toe part I8 pivotally .connected atrits rearward end to the front end of the rear part I4. The front end of the rear part I5 of the foot piece is provided with a transversely-extending, partly cylindrical end surface I9 and with upper and lower, transverselyextending radial shoulders 20 and 2I vsubstantially diametrically opposite each other. This rear part is also provided with two spaced-apart, substantially parallel slots 22 extending through the cylindrical surface I9 and the shoulders 2D and 2| and with an intermediate slot or groove 23 between the two slots 22.

The toe part I8 is provided in its rear end with a transversely-extending7 cylindrical concavity of substantially the same diameter as the partlycylindrical extension I 9 on the rear part I 6 of the foot piece and with spaced-apart, substantially parallel slots 24 and an intermediate groove 25 between the slots 24. A pair of at hinge tongues 26 is rigidly secured, one in each slot 24 of the toe part by suitable means, such as the two pins 27 extending transversely through the toe part and through the apertured end parts of the tongues 26 received in the slots 24. These tongues extend into corresponding slots 22 in the rear part I6 and have apertures near their rearward ends and a pivot pin 28 extends transversely through the rear part I6 of the foot piece near the front end of the latter and through the rearward ends of the tongues 26 to pivotally connect the toe part I8 to the rear part I4 of the foot piece I0. The toe part is provided with an upper shoulder 29 and a lower shoulder 30 disposed one at each edge of the partly-spherical, transverse concavity in the rearward end thereof, and these shoulders cooperate with the upper and lower shoulders 20 and 2| on the rear part of the foot piece to limit the extent of relative pivotal movement between the toe part I8 and the rear part I6 of the foot piece. This movement is of such an extent, as illustrated in .Figures 4,. 5 and 6, that the toe part 3 may move upwardly from a position in which it is substantially straight with the rear part I4, as illustrated in Figures 1 and '7, to a position in which it is sharply inclined upwardly relative to the rear part, as illustrated in Figure 6, which is substantially equivalent to the flexing of a natural foot between a standing and a kneeling position. It will be noted that the hinge tongues 26 are so shaped that they do not, atA any time, protrude below the bottom surface of the foot piece, and are of suficient cross-sectional area to provide adequate strength for the pivotal joint between the toe part and the rear part of the foot piece.

The hollow rear part I4 of the foot piece is preferably formed of a suitable light-weight metal, such as aluminum or a magnesium alloy, and is provided with a pair of upstanding lugs 3I disposed one at each side of the rear part of the foot piece and transversely opposed to each other.

Each of these lugs has on its rearward side and near its upper end a circular eye 32 receiving the annular outer race 33 of an anti-friction ball bearing, generally indicated at 34, and on the forward side of its upper end with an upward extension 35 having an upper end substantially perpendicular vto the longitudinal or vertical center-line of the lug and providing an upwardlyfacing shoulder 36. l

An inner race 3l is circumspatially disposed within the outer race 33 and bearing balls 38 are operatively disposed between the two races. The :Inner race is carried on the external surface of an apertured, circular boss 3S provided on one side of an arm 4Q riveted ori-otherwise vperma-wnently secured to a respective strut' bar 4i near the lower end of the latter.

as is clearly illustrated in Figure '8, and a washer 42 overlies the opposite sides of the two races. A tubular spacer 43, internally screw threaded near its opposite ends, is disposed between the two opposed arms 4e substantially concentric with the axis of the two anti-friction bearings 34 and a pair of screws 44 extend one through each washer 42, through the associated anti-friction bearing 34, and through the boss 3% and arm 40 and is threaded into the adjacent. end of the spacer 43 to secure the bearing parts together in operative assembly. A thrust `washer 44 is preferably interposed between the inner surface'of each arm 4i) and the adjacent end of the spacer 43 and the inner and outer bearing races are provided with grooves which are asymmetrical in.

surface substantially perpendicular to the longi-" tudinal center-line of the strut bar, Va portion 45 of which surface overlies the upwardly-facing shoulder 3G provided on the corresponding lug 3 I. Both of these shoulders are disposed at the forward side of the axis of the anti-friction bearings Slijand limit -the relative pivotal movement between the strut bars 4I and the rear part of the ioot piece i4, so that the strut bars cannot swing forwardly relative to thefoot piece beyond a position in which a plane including the longitudinal center-lines of both strutfbars is sub-l stantially perpendicular to a substantially hori-Y The arrri 40 overlies both bearing races-33 and 3'! at one side thereof,

zontal plane including the longitudinal centerline of the foot piece or, in other words, the strut bars cannot extend forwardly of a substantially vertical position without moving the foot piece when the foot piece is in flat contact with a horizontal supporting Surface, this limiting forward position of the strut bars being clearly illustrated in Figure 1. The Ytwo strut bars 4I are rigidly secured together at a location spaced above the arms 4i) or" `the anti-friction bearings 34 by a pair of spaced-apart, substantially parallel, transverse plates including an upper plate 46 and a lower plate 4l. Each of these plates is provided alongr opposite edges with upturned ears 48 which contact the inner surfaces of the respective strut bars and are rigidly secured to the strut bars by suitable means, such as the rivets 49. Plates 46 and 4? extend forwardly and rearwardly of the strut bars and are provided near their forward ends with registering apertures 56 and near their rearward ends or edges with registering apertures 5i. A pin 52 is slidably mounted in the apertures 58 and extends above and below the two plates 4e and 4'? and a similar pin 53 is slidably mounted in the apertures I. A coiled compression spring 54 surrounds a portion of pin' 52 above upper plate 4t bearing at its lower end on the upper surface of the plate 46 and at its upper end against an abutment washer 5'5 secured on the pin by a nut 5E threaded onto the externallyscrew-threaded upper end of the pin. A similar coiled compression spring 5l surrounds the portion of pin 53 above upper plate 46 bearing at its lower end on the upper surfaceof plate 46 and its upper end against an abutment washerl 518 secured on pin 53 by a nut 59 threaded'onto the externally-screw-threaded upper end of the pin.

A ilexible cable @il is secured at its upper end to the lower end of pin 52`by any suitable cablesecuring means, such as by extending the cable into a longitudinal well provided in the end of the pin and extending a transverse pin 5I through the pin and the cable above the lower end of the pin, and is secured at its lower end by an inverted, U-shaped stirrup 62 to the upper side of the rear part I4 of the foot piece just inwardly of the instep portion Il of such rear part. lVith this arrangement the force of spring 54 tends to pull the forward end of the foot piece upwardly until the shoulders 3% and 45 are in contact limiting such upward movement and resiliently resists pivotal movement of the foot piece relative 'to the strut bars 4I about the axis of pivot bearings 34 in a direction to turn the front portion of the foot piece downwardly and the heel upwardlyI as occurs when the artificial leg is swung forwardly to begin a new step, as is particularly illustrated in Figure 4. The spring 54 is sov adjusted by properly positioning nut .'56 that theheel can move upwardly a desired amount-under pressure when the leg is in the position illustrated in Figure 4, to cushion the 'impact of the heel with the supporting surface, vand to facilitate the stepping action of the mechanism.

As shown in Figure 4, the shoulders 36 fand 45 are separated, spring 54 is compressed, and spring 51 is expanded. A cable 63 is secured at its upper end to the lower end of pin 53 by suitable means, such as described above in connection with the upper end of cable 6U, and passes downwardly into the foot piece nearthe heel I5 thereof, and around a roller 64 mounted in the heel part of the foot piece for rotation about a transversely-extending pin 65. forwardly from the roller 64 and under ananti- The cable 6'3 extends piece up against the force of spring 54 and of resiliently holding the toe part of the foot piece down to itsposition lin which it is substantially straight with the rear part of the foot piece, as"

illustrated in Figure '7. The toe part is pivotally movable upwardly from its position in which lower shoulders 2| and 30 are in contact, to its position in which upper shoulders 20 and 29V are in contact by compression by spring 51. As soon as the upwardly-turning pressure is released from' the toe part, spring 51 will immediately return it to its loweror substantially straight position.

Thigh boot l 3 includes two substantially parallel, spaced-,apart strut bars to which are secured bearing 'arms 1l, similar in all respects to the arms 4and secured tothe strut bars byfsuitable rivets. These arms are provided with apertured bosses carrying respective ball bearing inner races andthe upper ends of the shank strut bars 4l are provided with circular eyes receiving respectively, the outer races of thel two bearings and anti-,friction balls are disposed between each inner and outer anti-friction. bearing race, as described above. AA tubular spacer sleeve 12 is disposed between the arms 1| concentric with thel bosses thereon and .thrust washers 13 are preferably interposed between the ends 0f this sleeve and the adjacent surfaces of the arms. A thrust washer 14 overlies the outer sides of each pair of ball bearing races, and a screw 15 extends through each outer washer, each inner race, each arm 1| and each thrust washer 13 and is threaded into the internally screw-threaded end of the tubular spacer to hold the corresponding bearing structure in operative assembly. The inner and outer races are preferably formed in the same manner as the races for'the bearings 34, described above, so that the lbearings may be tightened or preloaded lbyl tightening the screws 15. Each strut bar 4I is provided on its upper f end with a perpendicularly-extending shoulder 16 and each of the upper strut bars 10 is provided on its lower end with a corresponding shoulder 11, these two shoulders being disposed to one side of the axis of the upper anti-friction bearings to provide a knee joint in which the upper and lower strut bars are relatively movable in one direction about the axis of the anti-friction bearing, but have their relative movement in the opposite direction limited to a substantially vertical position in which the upper and lower strut bars are in substantially straight, longitudinal alignment with each other.

A coiled torsion spring 18 surrounds the spacer sleeve 12 and has one end 19 provided with a hook operatively engaging one of the lower strut bars 4| near the upper anti-friction bearing and its other end 8D provided with a hook operatively engaging the upper strut bar at the opposite side of the bearing assembly, this spring serving to resiliently urge the upper and lower strut bars to a substantially straight condition in which the respective shoulders 16 and 11 are in bearing engagement with each other.

A hollow shell 8l of suitable material, such as thin aluminum, surrounds the shankiportion of the artificial leg mechanism and is secured to the and supported thereby,` suitable strut bars 4I spacers being used, as may be foundl convenient,

to properly position the shell'on the .internalv mechanism. The lower end of this hollow shell- Overlies the upper portion` of the foot piece'l, as'- is clearly illustrated in Figure 1, so' that no-gaps Will lbe opened in the artificialleg by movement of the foot piece, as explained above. The thigh' boot may be 'of any desired construction andY rigidly secured to the upper strut bar 10 which may be made of any suitable length and shape to accommodate the wearer of the leg.

The two lower strut bars 4l are rigidly secured together by the plates 41 and 48 and by the lower anti-friction bearing assembly and together withv these plates and the bearing assembly constitute a unitary shank portion for the leg mechanism. The invention may be embodied in other specic forms without departing from the spirit or essential characteristics thereof. Y The present embodiment is, therefore, to be considered in all respects as illustrative and not restrictive, theA scope of the invention being indicated by the ap` pended claims rather vthan by the foregoingde-' scription, and all changes which come within the meaning and range of equivalency of the claims, embraced thereinl` .l

are, therefore, intended .to be W'hat is claimed is:

LMechanism vfor an articial leg..comprising a two-part foot piece, means hingedly connecting the two parts of "said foot piece together forl relative movement abouta substantially,transversef axis, a pair of spaced-apart'strut bars .'ups'tandl-i, ing from the rear part of said two-part footl piece,-means connecting the lower ends ofsaid strut bars to said foot piece for limited pivotal movement about an axisv substantially transverse to saidfoot piece, and spring means carried byl said. strut bars and operatively connected tolsaid foot piece to. resiliently control movement of said foot vpiece relative to said strut bars and movement of the two parts of said footpiece relative to each other, said means pivotally connecting said two parts of said Vfoot piececornprising a partly-cylindrical, transversely-extending pro?y trusion on the front end ofthe rear. part of saidA foot piece rotatably received ina partly-cylin v drical, transversely-extending socket in the rearward end of the toe part of said foot piece, a pair of transversely-extending shoulders on said rear part disposed one in the upper and one in the lower surface of the latter at the upper and lower edges of said protrusion, a pair of transverselyextending shoulders on said toe part disposed one at the upper and one at the lower edge of said socket and cooperating with said rear-part shoulders to limit movement of said toe part relative to said rear part in both directions, a pair of spaced-apart, substantially parallel hinge tongues secured in said toe part and having apertured ends extending into arm-receiving slots in said rear part, and a pivot pin extending transversely through said rear part and said hinge arms pivotally inter-connecting said foot-piece parts.

2. Mechanism for an artificial leg comprising a two-part foot piece, means hingedly connecting the two parts of said foot piece together for relative movement about a substantially transverse axis, a pair of spaced-apart strut bars upstanding from the rear part of said two-part foot piece, means connecting the lower ends of said strut bars to said foot piece for limited pivotal movement about an axis substantially transverse, to said foot ,pie-ce, and 'spring means carried by said strut bars and operatively connected to said foot piece to resiliently control movement of said foot piece relative to said strut bars and movement of t-he two parts of said foot piece relative to eachother, Ysaid. means connecting the lower ends of said strut bars to said foot piece comprising ya pair of transversely-opposed lugs upstandi-ng from the rear part of the foot piece and each having in its upper end a circular eye and an end sur-face providing a shoulder at the side of said eye corresponding to the front end of said foot piece, a pair of bearing arms each having an apertured boss thereon, a bearing outer race in the eye of -each lug, a bearing inner race on each boss rotatably received in a corresponding outer race, said bearing arms being secured one to each of said strut bars near the lower ends of the latter, a tubular spacer disposed between said bearing arms concentric with said apertured bosses, a washer at the outer side of each bearing assembly, and a respective screw extending through each outer washer and the corresponding bearing-arm boss and threaded into the adjacent end of the tubular spacer to secure said bearings in operative assembly.

3. Mechanism for an articial leg comprising a two-part foot piece, means hingedly connecting the twoparts of said foot piece together for relan tive movement about a substantially transverse axis, a pair of spaced-apart strut bars upstanding from the rear part of saidVtwo-part foot piece, means connecting the lower ends of said strut bars to said foot piece for limited pivotal movementabout an axis substantially transverse to said foot piece, and spring means carried by said strut bars and operatively connected to said foot piece to resiliently control movement of said foot piece relative to said strut bars and movement of the two parts of said foot piece relative to each other, said spring means comprising a pair of spaced-apart supporting plates secured between said strut bars and having aligned apertures therein, a pair of pins slidable in said supporting-plate apertures disposed one at the front and one at the rear side of said strut bars and substantially parallel to the latter, a respective coiled compression spring surrounding each pin above the upper supporting plate, an adjustable spring 8 abutment on/the upper end of each pin, a stirrup secured tothe rear part of said foot piece at the front side of said strut bars, a cable connecting said stirrup to the lower end of the pin at the front side of said bars to said stirrup, a roller in the rear part of said foot piece adjacent the heel end thereof, a cable connected to the lower end of the pin at the rear side of said bars, passing under said roller and secured at its opposite end to said toe part of said foot piece adjacent the bottom surface of the latter, and a roller carriedV by the means hingedly connecting said foot-piece parts together and bearing upon said last-mentioned cable.

4.- lMechanism .for an articial leg comprising a two-part lfoot piece, means hingedly connecting the twol parts of said foot piece together for relative movement about a substantially transverse axis, a pair of spaced-apart strut bars upstanding from the rear part of said two-part foot piece, means connecting the lower ends of said strut bars to said foot piece for limited pivotal movement about an axis substantially transverse to said foot piece, and spring means carried by said strut bars and operatively connected to said foot piece to resiliently control movement of said foot piece relative to said strut bars and movement of the two parts of said foot piece relative to each other, said spring means comprising a pair of springs carried by said strut bars and means connecting said springs to said foot piece, the

connecting means for one of said springs including a roller in the rearward end of said foot piece and a cable passing under lsaid roller and con- U nected tothe toe part of said foot piece nearv the bottom surface of the latter.

HANSEL SARTIN.

REFERENCES CITED lThe following references are of record in the iil'e of this patent:

UNITED STATES PATENTS Number Name Date 2,152,402 Davies Mar. 28, 1939 Y FOREIGN PATENTS Number Country Date 114,385 Great Britain Apr. 4, 1918 316,659 Germany Dec. 1, 1919 

